LT3825EFE#TRPBF Linear Technology, LT3825EFE#TRPBF Datasheet

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... The part also has load com- pensation, undervoltage lockout and soft-start circuity. L, LT, LTC, LTM, Burst Mode, SwitcherCAD, Linear Technology and the Linear logo are registered trademarks and No R trademarks are the property of their respective owners. Protected by U.S. Patents, including 6948466, 5841643 ...

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... Storage Temperature Range .................. –65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300°C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL LT3825EFE#PBF LT3825EFE#TRPBF LEAD BASED FINISH TAPE AND REEL LT3825EFE LT3825EFE#TR Consult LTC Marketing for parts specified with wider operating temperature ranges. ...

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ELECTRICAL CHARACTERISTICS junction temperature range, otherwise specifi cations are 90k 27.4k 90k, unless otherwise specifi ed. tON PGDLY ENDLY PARAMETER Reference Voltage Line Regulation Feedback Amplifier Voltage Gain Soft-Start Charging Current Soft-Start ...

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LT3825 TYPICAL PERFORMANCE CHARACTERISTICS V and V CC(0N) CC(OFF) vs Temperature CC(ON CC(OFF –50 – 100 TEMPERATURE (°C) 3825 G01 SENSE Voltage vs Temperature 110 ...

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TYPICAL PERFORMANCE CHARACTERISTICS Feedback Amplifier Output Current 125°C 25°C 50 –40° –10 –30 –50 –70 0.9 1 1.1 1.2 1.3 1.4 V (V) FB 3825 G10 Feedback Amplifier Voltage Gain vs Temperature 1700 1650 ...

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LT3825 TYPICAL PERFORMANCE CHARACTERISTICS Minimum PG On-Time vs Temperature 340 R = 158k tON(MIN) 330 320 310 300 290 280 270 260 –50 – 100 TEMPERATURE (°C) 3825 G19 PIN FUNCTIONS SG (Pin 1): Synchronous Gate ...

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PIN FUNCTIONS V (Pin 9): Pin used for frequency compensation for the C switcher control loop the output of the feedback amplifier and the input to the current comparator. Switcher frequency compensation components are normally placed on this ...

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LT3825 BLOCK DIAGRAM UVLO 19. – 1.237V 15.3V REFERENCE ( UVLO 10 I UVLO OSC 7 OSCILLATOR SYNC PGDLY 15 ENDLY 4 8 CLAMPS 0.7 + 1.3 – ...

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FLYBACK FEEDBACK AMPLIFIER LT3825 FEEDBACK AMP 1.237V – + COLLAPSE DETECT ENABLE TIMING DIAGRAM PRIMARY SIDE MOSFET DRAIN VOLTAGE PG VOLTAGE SG VOLTAGE V FLBK – PRIMARY ...

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LT3825 OPERATION The LT3825 is a current mode switcher controller IC de- signed specifi cally for use in an isolated fl yback topology employing synchronous rectifi cation. The LT3825 operation is similar to traditional current mode switchers. The major difference ...

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OPERATION that developed under these conditions, forced continuous operation normally occurs. See Applications Information for further details. Enable Delay (ENDLY) The fl yback pulse appears when the primary-side switch shuts off. However, it takes a fi nite time until the ...

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LT3825 OPERATION LOAD COMP – CMP CMP Figure 1. Load Compensation Diagram FB node. This effectively increases the voltage required at the top ...

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APPLICATIONS INFORMATION Transformer Design Transformer design/specification is the most critical part of a successful application of the LT3825. The following sections provide basic information about designing the transformer and potential trade-offs. If you need help, the LTC Applications group is ...

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LT3825 APPLICATIONS INFORMATION As a rough guide, leakage inductance of several percent (of mutual inductance) or less may require a snubber, but exhibit little to no regulation error due to leakage spike behavior. Inductances from several percent up to perhaps ...

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APPLICATIONS INFORMATION Ripple current and percentage ripple is largest at minimum duty cycle; in other words, at the highest input voltage calculated from • MAX ( ) MIN IN ...

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LT3825 APPLICATIONS INFORMATION Setting Feedback Resistive Divider The expression for V developed in the Operation sec- OUT tion is rearranged to yield the following expression for the feedback resistors: ( ⎛ ⎡ +I • ESR + R V ⎣ ⎜ ...

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APPLICATIONS INFORMATION 4. Compute: R SENSE = • • • CMP OUT ( ) 5. Verify this result by connecting a resistor of this value from the R pin to ground. ...

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LT3825 APPLICATIONS INFORMATION The t resistor is set with the following equation: ON(MIN) t (ns) – 104 ON(MIN) (kΩ tON(MIN) 1.063 Keep R greater than 70k. A good starting value tON(MIN) is 160k. Enable Delay Time (ENDLY) Enable ...

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APPLICATIONS INFORMATION The bias current on this pin depends on the pin volt- age and UVLO state. The change provides the user with adjustable UVLO hysteresis. When the pin rises above the UVLO threshold a small current is sourced out ...

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LT3825 APPLICATIONS INFORMATION Switching action commences and the converter begins to deliver power to the output. Initially the output voltage is low and the flyback voltage is also low the LT3825 current (only a fraction comes from ...

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APPLICATIONS INFORMATION next cycle. This action naturally holds the V during the current comparator sense action (current mode switching). AN19 provides a method for empirically tweaking frequency compensation. Basically it involves introducing a load current step and monitoring the response. ...

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LT3825 APPLICATIONS INFORMATION Output Voltage Error Sources The LT3825’s feedback sensing introduces additional sources of errors. The following is a summary list. The internal bandgap voltage reference sets the reference voltage for the feedback amplifier. The specifications detail its variation. ...

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APPLICATIONS INFORMATION For each secondary-side power MOSFET RMS current is given by OUT I RMS SEC ( ) 1 – DC MAX Calculate MOSFET power dissipation next. Because the primary-side power MOSFET operates at high V tion power ...

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LT3825 APPLICATIONS INFORMATION Synchronous Gate Drive There are several different ways to drive the synchronous gate MOSFET. Full converter isolation requires the synchro- nous gate drive to be isolated. This is usually accomplished by way of a pulse transformer. Usually ...

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APPLICATIONS INFORMATION charging/discharging ΔV. This percentage ripple changes, depending on the requirements of the application. You can modify the equations below. For a 1% contribution to the total ripple voltage, the ESR of the output capacitor is determined by: ( ...

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LT3825 APPLICATIONS INFORMATION The total IC dissipation is computed as • • (Q D(TOTAL OSC V is the worst-case LT3825 supply voltage. CC Junction temperature is computed as: • θ ...

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APPLICATIONS INFORMATION Place the small-signal components away from high frequency switching nodes. This allows the use of a pseudo-Kelvin connection for the signal ground, where high di/dt gate driver currents flow out of the IC ground pin in one direction ...

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LT3825 TYPICAL APPLICATIONS + V IN 36V TO 72V 2.2μF 100V BAS21 402k 29. 20Ω UVLO PGDLY 3.01k 15k 12k 100k ALL CAPACITORS 25V UNLESS OTHERWISE NOTED T1: EDFD25-3F3 GAP ...

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TYPICAL APPLICATIONS + V IN 36V TO 72V 0.82μF 100V BAS21 402k 26. 20Ω FB UVLO PGDLY 15k 3.01k 15k 100k Efficiency vs Load Current 90 36V IN 88 72V IN 48V IN ...

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LT3825 TYPICAL APPLICATIONS + V IN 36V TO 72V 28. • 3.01k 1% 402k 1% FB 2.2μF 100V UVLO 15k 1% PGDLY t SYNC R ON 12k 100k 750Ω C4: TDK C3225X5R0J476M C5: SANYO 6TPD470M L1: ...

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... A J Addition to Note 3 Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. LT3825 PAGE NUMBER ...

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... DFN-8, MSOP-8E www.linear.com ● 3.58 (.141 6.40 2.94 (.252) (.116) BSC 1.10 (.0433) MAX 0.05 – 0.15 (.002 – .006) FE16 (BC) TSSOP 0204 ® ≤ 36V, Burst Mode Operation IN LT 0110 REV C • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 2007 3525fc ...